1. Field of the Invention
The present invention relates to a cable insert nozzle that is suitable as a nozzle of a manipulator for inserting a cable associated with a sensor into a heat-exchanger tube in non-destructive inspection of various types of heat-exchanger tubes.
2. Description of the Prior Art
For non-destructive inspection of heat-exchanger tubes of thermal power installations and atomic power, supersonic defect hunting and eddy current defect hunting have been generally employed, and in either of such defect hunting processes, inspection is carried out by inserting a cable associated with a float having a sensor at its tip end into the heat-exchanger tubes through other end portions thereof with the aid of pressurized water or compressed air.
FIG. 8 shows the state where a cable associated with a float is being inserted into a heat-exchanger tube via a nozzle of a manipulator, that is brought into press contact with a tube end portion of the heat-exchanger tube (header plate), with the aid of pressurized water or compressed air. One example of the cable insert nozzle of the prior art now will be explained with reference to FIG. 8.
In FIG. 8, a heat-exchanger tube 1 is subjected to seal welding 3 after it has been inserted into a counter-bored portion of a header plate 2. A nozzle portion of a manipulator is divided into a female die 4 and a male die 5 of spherical type which are coupled together by means of a nozzle holder 6 and nozzle cap screws 7. On a seat surface of the female die 4 is mounted a packing 8 made of rubber for the purpose of preventing leakage of pressurized water or compressed air.
The above-described female die 4 and male die 5 have extending therethrough cable insert holes 4a and 5a, respectively. At the front or inner portion of female die 4 is provided an opening 4b for projection therethrough of a cable. Further more, on a cable 9 is mounted a float 9a for the purpose of generating a thrust force for transporting (inserting and retracting) the cable 9. It is to be noted that the characteristic feature of the illustrated nozzle resides in that the nozzle is divided into two parts and a spherical seat is provided. Thereby, even in the event that deviation of the axis of the nozzle due to flexure of the manipulator should arise, sealing between the end portion of the tube and the packing 8 can be maintained.
FIG. 9 shows the state where the nozzle has been brought into press contact with a tube end portion after the manipulator was moved by one pitch for the purpose of inspection of the next tube. The nozzle in the prior art lacked the capability of restoring the female die 4 to alignment with the axis of the male die 5 upon separating the nozzle from the tube end portion after completion of an inspection. Therefore, upon inserting the nozzle or moving the nozzle by one pitch, the axes of the female die 4 and the male die 5 may deviate from each other. This, even if the nozzle is moved by one pitch according to drawings for manufacture of the heat-exchanger, it is difficult to insert the nozzle into the next tube end portion.